In an image information chip or the like, a multi-port SRAM is embedded with a logic circuit. When the 3 port is used, the 1 port may serve as a differential write and readout port, and the 2 port may serve as a single ended readout dedicated port. While the occupied area of an embedded SRAM can be reduced, the number of write and readout ports is limited to only one, and readout characteristics as fast as differential readout cannot be expected in single ended readout. A new arrangement is therefore provided in which three differential write and readout ports are included in a memory cell structure of the embedded SRAM, an N-well region, for example, is arranged at the center of a cell, and a P-well region is arranged on both sides thereof.
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1. A semiconductor integrated circuit device comprising: (a) a semiconductor substrate having a first main surface; (b) an embedded SRAM region which is provided on the first main surface side of the semiconductor substrate; (c) a memory cell arrangement region which is provided within the SRAM region; and (d) a large number of memory cell regions which are provided in a matrix within the memory cell arrangement region; wherein each memory cell region includes (d1) a first well region having a first conductivity type; (d2) a second well region and a third well region having a second conductivity type which are provided on both sides of the first well region; (d3) a first bit line and a second bit line that form a mutually complementary pair; (d4) a third bit line and a fourth bit line that form a mutually complementary pair; (d5) a fifth bit line and a sixth bit line that form a mutually complementary pair; (d6) a data storage unit; (d7) a first storage node which is provided in the data storage unit; (d8) a second storage node, provided in the data storage unit, which is complementary to the first storage node; (d9) a first driver MISFET, provided in the data storage unit and the second well region, of which one of the source drain terminals thereof is connected to the first storage node; (d10) a second driver MISFET, provided in the data storage unit and the third well region, of which one of the source drain terminals thereof is connected to the second storage node; (d11) a first access MISFET, provided in the second well region, of which one of the source drain terminals thereof is connected to the first storage node and the other thereof is connected to the first bit line; (d12) a second access MISFET, provided in the third well region, of which one of the source drain terminals thereof is connected to the second storage node and the other thereof is connected to the second bit line; (d13) a third access MISFET, provided in the second well region, of which one of the source drain terminals thereof is connected to the first storage node and the other thereof is connected to the third bit line; (d14) a fourth access MISFET, provided in the third well region, of which one of the source drain terminals thereof is connected to the second storage node and the other thereof is connected to the fourth bit line; (d15) a fifth access MISFET, provided in the second well region, of which one of the source drain terminals thereof is connected to the first storage node and the other thereof is connected to the fifth bit line; and (d16) a sixth access MISFET, provided in the third well region, of which one of the source drain terminals thereof is connected to the second storage node and the other thereof is connected to the sixth bit line.
A semiconductor integrated circuit device, such as an image information chip, has an embedded SRAM region on a semiconductor substrate. Within this SRAM region is a memory cell arrangement consisting of multiple memory cell regions arranged in a matrix. Each memory cell includes a first well region of a first conductivity type (e.g., N-well) with second and third well regions of a second conductivity type (e.g., P-well) on either side. Each cell also includes three pairs of complementary bit lines (six total: first/second, third/fourth, fifth/sixth), a data storage unit, first and second storage nodes (complementary), a first driver MISFET in the second well connected to the first storage node, a second driver MISFET in the third well connected to the second storage node, and six access MISFETs, two in each of the second and third wells, connecting the storage nodes to the bit lines.
2. The semiconductor integrated circuit device according to claim 1 , wherein each memory cell region further includes: (d17) a first active region that has the first driver MISFET and the first access MISFET formed therein, and has a rectangular shape extending into the second well region; (d18) a second active region that has the third access MISFET and the fifth access MISFET formed therein, and has a rectangular shape extending into the second well region; (d19) a third active region that has the second driver MISFET and the second access MISFET formed therein, and has a rectangular shape extending into the second well region; and (d20) a fourth active region that has the fourth access MISFET and the sixth access MISFET formed therein, and has a rectangular shape extending into the second well region, the first to fourth active regions being oriented such that longitudinal directions thereof are the same.
The semiconductor integrated circuit device described as having an embedded SRAM with memory cells containing three pairs of bit lines and driver/access MISFETs, further includes active regions within each memory cell. Specifically, a first active region within the second well region contains the first driver MISFET and the first access MISFET and has a rectangular shape. A second active region within the second well region contains the third access MISFET and the fifth access MISFET, also rectangular. A third active region within the second well region contains the second driver MISFET and the second access MISFET, rectangular. A fourth active region within the second well region contains the fourth access MISFET and the sixth access MISFET, rectangular. All four active regions have the same longitudinal orientation.
3. The semiconductor integrated circuit device according to claim 2 , wherein each memory cell region further includes: (d21) a first local interconnect that interconnects impurity regions of the first active region and the second active region; and (d22) a second local interconnect that interconnects impurity regions of the third active region and the fourth active region.
The semiconductor integrated circuit device described as having an embedded SRAM with memory cells containing three pairs of bit lines, driver/access MISFETs, and rectangular active regions, also includes local interconnects. A first local interconnect connects impurity regions within the first and second active regions (containing the first driver/access MISFETs and third/fifth access MISFETs). A second local interconnect connects impurity regions within the third and fourth active regions (containing the second driver/access MISFETs and fourth/sixth access MISFETs).
4. The semiconductor integrated circuit device according to claim 3 , wherein a width of the first active region is larger than a width of the second active region, and a width of the third active region is larger than a width of the fourth active region.
The semiconductor integrated circuit device described as having an embedded SRAM with memory cells containing three pairs of bit lines, driver/access MISFETs, rectangular active regions with local interconnects, has specific active region width characteristics. The width of the first active region (containing the first driver and first access MISFETs) is larger than the width of the second active region (containing the third and fifth access MISFETs). Similarly, the width of the third active region (containing the second driver and second access MISFETs) is larger than the width of the fourth active region (containing the fourth and sixth access MISFETs).
5. The semiconductor integrated circuit device according to claim 1 , wherein the first driver MISFET, the second driver MISFET, the first access MISFET and the second access MISFET have threshold voltages higher than those of the third access MISFET, the fourth access MISFET, the fifth access MISFET and the sixth access MISFET.
The semiconductor integrated circuit device described as having an embedded SRAM with memory cells containing three pairs of bit lines and driver/access MISFETs, has differing threshold voltages for different transistors. The first and second driver MISFETs and the first and second access MISFETs have higher threshold voltages compared to the third, fourth, fifth, and sixth access MISFETs. This implies different performance characteristics for the different sets of access transistors within the SRAM cell.
6. The semiconductor integrated circuit device according to claim 1 , wherein a planar positional relationship between the third access MISFET and the fifth access MISFET in a predetermined direction and a planar positional relationship between the fourth access MISFET and the sixth access MISFET in the predetermined direction are mutually reversed.
The semiconductor integrated circuit device described as having an embedded SRAM with memory cells containing three pairs of bit lines and driver/access MISFETs, has a specific arrangement of the third/fifth and fourth/sixth access MISFET pairs. The planar positional relationship of the third and fifth access MISFETs in a certain direction is reversed compared to the planar positional relationship of the fourth and sixth access MISFETs in the same direction. This describes a physical layout characteristic of the SRAM cell.
7. The semiconductor integrated circuit device according to claim 3 , wherein each memory cell region further includes: (d23) a first pull-up MISFET, provided in the data storage unit and the first well region, of which one of the source drain terminals thereof is connected to the first storage node; (d24) a second pull-up MISFET, provided in the data storage unit and the first well region, of which one of the source drain terminals thereof is connected to the second storage node; and (d25) a power supply wiring which is connected to the other terminals of the first pull-up MISFET and the second pull-up MISFET, and is constituted by a first embedded wiring.
The semiconductor integrated circuit device described as having an embedded SRAM with memory cells containing three pairs of bit lines, driver/access MISFETs, rectangular active regions with local interconnects, additionally includes pull-up transistors. The device includes a first pull-up MISFET in the first well region connected to the first storage node, a second pull-up MISFET in the first well region connected to the second storage node, and a power supply wiring (first embedded wiring) connected to the other terminals of both pull-up MISFETs.
8. The semiconductor integrated circuit device according to claim 1 , wherein each memory cell region further includes: (d23) a first pull-up MISFET, provided in the data storage unit and the first well region, of which one of the source drain terminals thereof is connected to the first storage node; and (d24) a second pull-up MISFET, provided in the data storage unit and the first well region, of which one of the source drain terminals thereof is connected to the second storage node, and wherein all the MISFETs constituting each memory cell region are constituted by a fin type FET.
The semiconductor integrated circuit device described as having an embedded SRAM with memory cells containing three pairs of bit lines and driver/access MISFETs, includes pull-up transistors and uses FinFET technology. The device has a first pull-up MISFET in the first well region connected to the first storage node and a second pull-up MISFET in the first well region connected to the second storage node. All MISFETs within each memory cell region are FinFETs (fin-type field-effect transistors).
9. The semiconductor integrated circuit device according to claim 8 , wherein the first access MISFET and the second access MISFET are constituted by a fin type parallel FET.
The semiconductor integrated circuit device that has an embedded SRAM with memory cells containing three pairs of bit lines and uses FinFET technology for all transistors including pull-up devices, specifies that the first and second access MISFETs are constructed as fin-type parallel FETs.
10. The semiconductor integrated circuit device according to claim 8 , wherein the first driver MISFET, the second driver MISFET, the first access MISFET, and the second access MISFET are constituted by a fin type parallel FET.
The semiconductor integrated circuit device that has an embedded SRAM with memory cells containing three pairs of bit lines and uses FinFET technology for all transistors including pull-up devices, specifies that the first and second driver MISFETs and the first and second access MISFETs are constructed as fin-type parallel FETs.
11. The semiconductor integrated circuit device according to claim 1 , wherein (x1) the third bit line and the fourth bit line of each memory cell region are different from the third bit line and the fourth bit line of a memory cell region adjacent to the memory cell region in a predetermined direction, and (x2) the fifth bit line and the sixth bit line of each memory cell region are different from the fifth bit line and the sixth bit line of a memory cell region adjacent to the memory cell region in the predetermined direction.
The semiconductor integrated circuit device described as having an embedded SRAM with memory cells containing three pairs of bit lines and driver/access MISFETs, has a specific bit line arrangement. The third and fourth bit lines of each memory cell region are different from the third and fourth bit lines of an adjacent memory cell region in a given direction. The fifth and sixth bit lines of each memory cell region are also different from the fifth and sixth bit lines of a neighboring memory cell region in the same direction. This describes a bit line multiplexing scheme.
12. The semiconductor integrated circuit device according to claim 11 , wherein each memory cell region or any memory cell region which is vertically adjacent thereto further includes: (d26) a first word line that extends within the memory cell region, and controls the first access MISFET and the second access MISFET of the memory cell region; (d27) a second word line that extends within a memory cell region adjacent to a vertical direction of the memory cell region, and controls the third access MISFET and the fourth access MISFET of the adjacent memory cell region and the memory cell region; and (d28) a third word line that extends within the memory cell region, and controls the fifth access MISFET and the sixth access MISFET of the memory cell region and a memory cell region which is vertically adjacent to the memory cell region.
The semiconductor integrated circuit device described as having an embedded SRAM with memory cells containing three pairs of bit lines, driver/access MISFETs, and a specific bit line arrangement (where the third/fourth and fifth/sixth bit lines differ from adjacent cells), also includes word lines. The cell or its vertically adjacent cell includes: a first word line controlling the first and second access MISFETs, a second word line in the vertically adjacent cell controlling the third and fourth access MISFETs of both the cell and its adjacent cell, and a third word line controlling the fifth and sixth access MISFETs of both the cell and its adjacent cell.
13. The semiconductor integrated circuit device according to claim 2 , wherein widths of the first active region, the second active region, the third active region and the fourth active region are equal to each other.
The semiconductor integrated circuit device described as having an embedded SRAM with memory cells containing three pairs of bit lines, driver/access MISFETs, and rectangular active regions, specifies that the widths of all the active regions are equal. The widths of the first, second, third, and fourth active regions within each memory cell are the same.
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October 30, 2016
July 18, 2017
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